1. Field of the Invention
The present invention relates to a 2,4-dihydroxyadipic acid derivative, a process for preparing the same and a process for converting the same to 3,5,6-trihydroxyhexanoic acid derivative.
The 2,4-dihydroxyadipic acid derivative is a novel compound which is useful as a common intermediate in the synthesis of a series of HMG-CoA (hydroxy methyl glutarylCoA) reductase inhibitors which are attractive as having a function of antihyperlipemia.
2. Description of the Related Art
Hitherto, no 2,4-dihydroxyadipic acid derivative has been synthesized, or there is no report on the use of the 2,4-dihydroxyadipic acid derivative in the production of the HMG-CoA reductase inhibitors. As an intermediate in the synthesis of the HMG-CoA reductase inhibitor, 3,5,6-trihydroxyhexanoic acid derivative has been mainly used. For the synthesis of the 3,5,6-trihydroxyhexanoic acid derivative, there are known a process comprising reacting an enolate of an acetate or its equivalent with a 3,4-dihydroxybutyric acid derivative to increase the number of carbon atoms and reducing the resulting 5,6-dihydroxyhexanoic acid derivative (cf. Japanese Patent Kokai Publication Nos. 22056/1988 and 199945/1989) and a process utilizing asymmetric epoxidation of allyl alcohol (cf. Tetrahedron Letters, 25, 3391 (1984)). For the synthesis of 3,5-dihydroxy-6-oxohexanonate derivative, there are known a process comprising oxidation of 3,5,6-trihydroxyhexanoate derivative (cf. Japanese Patent Kokai Publication No. 199945/1989) and a process comprising oxidation of a styrene derivative with ozone (cf. J. Med. Chem., 33, 2982 (1980)).
However, the above processes are not necessarily practical processes for the industrial production of 3,5,6-trihydroxyhexanoic acid derivative, since, for example, the process utilizing the 3,4-dihydroxybutyric acid derivative has a drawback that comparatively expensive reagents and complicated procedures are required for the, protection and deprotection of the hydroxy groups, and the process utilizing the asymmetric epoxidation of allyl alcohol has a drawback that it is difficult to selectively obtain a (3R,5S) isomer having a high activity as the HMG-CoA reductase inhibitor.